Automatic Processing with GAMIT

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Automatic Processing with GAMIT

• sh_gamit

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Overview

• Motivation for sh_gamit
• an automatic processing script
• runs GAMIT from RINEX files to H-files
• How to set up sh_gamit
• Running sh_gamit
• Getting input correct makes runs more robust
• Options in sh_gamit
• User controls

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Motivation for sh_gamit

• Increase in amount of GPS data
• requires autonomous processing
• GAMIT uses many files
• sh_gamit manages them automatically
• Successful with both continuous and campaign data

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What sh_gamit does

• Checks tables (e.g. polar motion/UT1) for valid
  time range
• Creates any directories that are needed.
• Begins execution in the processing directory.
• Get new tables by ftp if needed
• Checks orbit files by ftp if needed

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What sh_gamit does (2)

• Finds raw data files and translates them into
  RINEX format using teqc
• Finds RINEX-format data files
• Gets any missing files from the ftprnx entries
  with ftp
• Creates a daily processing directory
• Creates links in day directory to data files
• Executes GAMIT run in day directory

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What sh_gamit does (3)

• Plots one-way phase residuals and converted to
  images in GIF format
• optional
• GIF files are much smaller than postscript files
• Updates processing history file

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What sh_gamit does (4)

• Sends an email message to you (not Simon!) with
  important summary information
• number of sites
• disk space remaining
• best and worse RMS scatters
• RMS fit from GAMIT runs
• sites with large or no adjustments

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What sh_gamit does (5)

• Compresses, archives or deletes intermediate
  files as selected by the user.
• Begins processing next days data
• Continues until fatal error or all requested days
  are processed.

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What sh_gamit does not do

• Estimate velocities
• The dishes
• Think

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Basic example

• sh_gamit -d 1998 240 -orbit SIOF -expt emed
  -eops usno
• process GPS data from day 240 of 1998 (Aug 28)
• use any data in the local rinex directory
• ftp data for sites specified by the user
• optionally scan multiple directories to find data
• use Final orbit estimate from Scripps Institution
  of Oceanography (SIO)
• use EOP data from US Naval Observatory (USNO)
  IERS Bulletin A
• Name the run emed"
• identify files
• select data

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Running sh_gamit

• List options
• sh_gamit -help
• Select days of data to process
• -d yr days
• where yr and days are the data to be processed
  e.g., -d 1997 153 156 179
• -s yr d1 d2
• where d1 is start day and d2 is stop day to be
  processed e.g. 1997 153 178
• -r day
• where day is number of days before current date.

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sh_gamit options

• -expt
• 4 char name of experiment/solution being run
  Default expt
• -orbit
• Type of orbit to use. Default SIOF. Optional
  second argument gives the day-of-year for the
  orbit if not the same as processing day
• -orbt
• 4 char ID for orbit files. Default 4 char
  extracted from the orbit selected
• -eops
• Name of EOP series to use. (bull_b, bull_a,
  etc.) Default usno

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sh_gamit options (2)

• -sessinfo
• Session - sampling interval, number of epochs,
  start time (default 30 2880 0 0)
• -rx_doy_plus n
• Search RINEX file names this many days into the
  future for current-day data
• -rx_doy_minus n
• Search RINEX file names this many days into the
  past for current-day data
• -xsite list
• List of sites to be excluded from the processing.
  

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sh_gamit options (3)

• -netext ltchargt
• add network suffix ltchargt to day directories.
  i.e. 035r
• -yrext
• add year prefix to day directories. Ie
  1997_053
• -pres
• Plot gamit residuals as skyplots
  ltY/N/Egt. YES, NO, ELEV. Default N
• -nogifs
• Do NOT create skyplot GIF graphics files

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sh_gamit options (4)

• -copt file types
• Compress remaining files for each dayserve when d
  Default x k autcln.out
• -aopt file types
• Copy the specified files for each day to the
  directory specified by archivepth
• -dopt file types
• Delete specified files after processing each day.
  Default c
• -mailto
• Name of user and machine to send results
  summary. (e.g., simon_at_wegener.mit.edu)

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sh_gamit options (5)

• -snrres
• Calculate theoretical phase residuals from SNR.
  Requires raw data or RINEX with valid SNR values.
• -noacc
• Do not exclude satellites base on accuracy codes
  in the .sp3 file. Default exclude
• -xver char
• 1-character x-file version (6th character of
  x-file). Default is single-digit year
• -noftp
• Use this option if no ftp download connections
  are available.

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sh_gamit options (6)

• -remakex Y/C/N
• Y - Remake x-files without checking.
• C - Remake x-file if orbit and session.info
  are incompatible and all RINEX files are
  available Default C
• N - Don't remake x-files under any
  circumstances

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sh_gamit options (summary)

• Most of the sh_gamit options are not normally
  used and are related to processing old GPS data
  or reprocessing 'failed' days.
• Main options will be used in tutorial

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Before running sh_gamit

• Create and fill templates directory
• cd expt cp -r /gg/templates .
• Modify your files
• cd expt/templates
• edit templates/process.defaults
• edit templates/sites.defaults
• Create and fill "local" data directories
• mkdir rinex
• mdir raw
• Ready to go

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process.defaults

• Normally only needs a little modification
• Default mailto address
• Change directories where rinex and raw data may
  be found
• Change the paths to
• gs (ghostscript)
• convert (ImageMagik program to convert postscript
  to gif images).
• These changes could be made permanently at each
  institution. They depend on machine setup)

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sites.defaults

• File specifies other sites to be used in
  processing and how sites should be treated.
• Format
• site expt options
• expt is 4-character code for experiment
• options given below
• Main options
• ftprnx - ftp Rinex data
• ftpraw - ftp raw dat

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Options in sites.defaults

• localrx
• Used to name sites that should be used from local
  rinex directories. If given only these sites are
  processed from the found files
• xsite
• Used to name sites that should not be used or not
  used for certain time spans
• xstinfo
• Ignore this site while automatically updating
  station.info file after successful solution
• If a site is not in this list, then information
  about the antenna type and height will be
  extracted from the RINEX file

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How high was that antenna?

• If the station.info file is absent from the
  tables directory, then sh_gamit will use the
  header information from the RINEX file
• The file called guess_rcvant.dat will be used to
  translate the entries in the RINEX file to codes
  that GAMIT knows.
• If this fails, then GAMIT will stop 'fatally'
• Antenna height errors can be corrected downstream
  in GLOBK, but errors in identifying the antenna
  type can not be corrected (phase center
  variations)

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Controlling GAMIT

• Two main files may need to be changed depending
  on data being processed
• sestbl.
• sets parameters for the sessions being
  processed
• sittbl.
• sets parameters for individual sites and
  defaults for sites
• Both files reside in the tables directory
• Links in day directories point to them.
• Standard example versions of these files are
  for regional, bias fixed solutions.

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Apriori station coordinates

• Estimating them is a multi-step process
• generated from GLOBK (.apr) format apriori file
  with positions and velocities for each day
• GAMIT reads L-file with geocentric spherical
  lat/long/radius but no time dependence
• Apriori coordinates need to be good (discussed
  Lecture 3)

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Summary

• The sh_gamit script provides a robust method for
  processing GPS data automatically and
  autonomously
• Initial setup sometimes has problems, but once
  the first day of data runs without an error, the
  remaining days usually follow easily